1. Field of the Invention
This invention relates to a cap having a valve built therein. More particularly, the invention relates to caps such as a fuel cap or a radiator cap for an automobile, which is installed on an aperture of a container such as a fuel tank or a radiator and adjusts pressure in the container.
2. Description of the Prior Art
A Cap having a valve built therein is disclosed in U.S. Pat. No. 4,726,488.
A conventional cap having a valve therein comprises a cap body and a valve body. In the cap, an annular seal member is provided with an inner lip element and an outer lip element. The lip elements project in the same direction. An inner coil spring and an outer coil spring are disposed on opposite sides of the lip elements, and both coil springs align with the inner lip element and the outer lip element. A cap with a valve includes a seal member disposed in a fluid flow path of a cap body and urged against a prescribed seal portion. The seal member is of a disk-like form or ring-form. Further, the seal member is provided with lip elements that project the entire circumference of the peripheral surface and the lip elements have a constant length at a rear side. Unlike the present invention, there is no real valve subassembly within the cap.